A flip chip package has a small size and has superior electric characteristic and reliability in comparison with a package formed by a wire bonding technique. The flip chip package is obtained by directly bonding a semiconductor chip and a printed circuit board (PCB) substrate by using a metallic bump. Gold, copper and solder, etc. are applied as the metal bump. Among these, a flip-chip using a gold bump is typically bonded to a substrate by using conductive adhesives. Different from a chip using solder bumps, such a flip chip using the gold bump has recently been popular in a display field because it doesn't include harmful element such as lead to environment and human health and has superior bonding reliability.
A method for forming a gold bump includes an electroplating method, a vacuum depositing method, and a method forming a stud bump by wire bonding. Among these, the electroplating is most advantageous due to a simple manner and the low manufacturing costs.
A research for manufacturing a gold bump of a flip chip by using this electroplating method has been actively proceeded. For example, Korean patent publication NO. 10-2006-0044929 discloses a method for improving non-uniformity of a thickness of the gold bump in such a manner that metal with a low melting point is plated on a bump formed by plating or an alloy having a dome shape is formed thereon. However, after a formation of a gold bump by electroplating, the entire metallic seed layer, except for the gold bump, is etched so that only the gold bump remains on a wafer. Therefore, there is a disadvantage in that it is impossible to evaluate the electrical characteristics of the gold bump and a flip chip package bonded through electrical connection with the gold bump.
Korean patent registration NO. 10-0574986 discloses a method for forming a bump through an electroplating for a flip chip connection. A seed layer is formed for electroplating, and a shielding layer and a photosensitive mask are formed on the seed layer. Then, the exposed shielding layer, which has undergone a photolithography process and a developing process, is removed through dry etching, and a bump is formed on the exposed seed layer according to a plating method.
However, in the method according to the invention, the gold bump is formed by electroplating after the metal patterning and the shielding layer are formed. Therefore, it is necessary that an electrode wiring for forming the gold bump is formed when the metal pattern is formed, or a metallic seed layer for plating is formed and moved on a top of an insulating layer. Typically, the electrode wire is an unnecessary metal wire in an actual chip so that it has to be removed again after the gold bump is formed. Therefore, an additional process is necessary before and after the gold bump is formed thereby causing inconvenience.
As a similar example, a method for manufacturing a gold bump on an aluminum substrate by an electroplating method is announced [reference: John H. Lau, C. P. Wong, Ning-Cheng Lee, 0. W. Ricky Lee, Electronics Manufacturing with Lead-free, Halogen-free, and Conductive-adhesive materials, 4.1-4.9 (2003)]. The process as shown in FIG. 1 is performed in the announced reference. That is, according to the method, an insulating layer is formed on an aluminum pad and the top of the pad, and a metal seed layer for electroplating of a gold bump is formed again on the upper part of the insulating layer. Then, after a formation of the gold bump, the metal seed layer applied for plating is finally removed. Similar to the disclosed invention, this method requires forming and removing process of a metal seed layer to perform electroplating, and, thus, a manufacturing procedure becomes too complicated. Also, conventionally, a mask for photolithography, which is used for plating the gold bump, and a mask for photolithography, which is used in patterning an insulating layer formed on the top of a conductive film, are separately manufactured.
The above information disclosed in this Background Art section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.